This invention relates to die-cutting apparatus. More particularly, this invention relates to apparatus for mounting a die sheet in surface-to-surface contact with a die roller.
Equipment for cutting and scoring continuous webs of material, such as paper, sheet metal, cardboard and the like, typically include a pair of high-speed rotary cylinders that carry one or more working elements that operate on the webs as they are fed between the cylinders. In certain applications, the working elements are formed from thin flexible metal sheets that are designed to be mounted on the outside surface of the rotary cylinders. Each metal sheet, often called a die plate, has an array of cutting and scoring elements formed on the outside surface thereof and is normally mounted on a roller that is in synchronous rolling opposition with a second roller carrying a second sheet. The array of cutting and scoring elements on the two sheets are correspondingly formed so that they functionally mate to work against each other on opposite sides of the web as it passes between the rollers. One of the most critical problems confronting developers of such equipment has been the development of simple yet effective means for mounting the flexible die plates on the outside surface of the rollers. More specifically, developers have long recognized the need for rollers having mounting structures that are capable of accurately mounting the sheets in precise surface-to-surface contact on the outside surface thereof.
One example of a prior art apparatus that addressed this need may be found in U.S. Pat. No 4,187,752. In the '752 patent, the roller has a channel formed in its outside surface into which the ends of the sheets that constitute the die plate are inserted. Means are provided in the channel for gripping the sheet and pulling it into surface-to-surface contact with the roller. Bridging elements are mounted across the channel so that continuous cuts may be made. Although this and other prior art structures have served the purpose, they have not proved entirely satisfactory under all conditions of service for the reason that considerable difficulty has been experienced as a result of the complex structures employed therein as exemplified by the channel-bridging-gripping structures of the '752 patent. As such, attempts have been made by those skilled in these arts to develop simpler structures that eliminate the need for bridges and like devices. However, most attempts at eliminating the bridges have resulted in still more complex gripping structures that are often cumbersome to use and expensive to employ.